1. Field of the Invention
This invention relates to a nailing machine for driving in fasteners such as nails.
2. Description of the Related Art
FIGS. 14 and 15 show a conventional nailing machine. FIG. 14 shows an initial state of the nailing machine and FIG. 15 shows the nailing machine in operation.
As shown in FIG. 14, a machine body 1 includes an accumulator chamber 2 for accumulating compressed air, a cylinder 4, a piston 8 vertically movably supported in the cylinder 4, a drive bit 7 integrally formed with the piston 8, the lower end of which is used to drive in nails 6 positioned in an ejection portion 12, a return air chamber 3 that is provided on the lower outer periphery of the cylinder 4 and communicates with the interior of the cylinder 4 via an air passage 11 having a check valve, a main valve 5 vertically movably provided above the cylinder 4, a trigger valve 14 for providing and withholding the communication between a main valve upper chamber 15 and the accumulator chamber 2 via an air passage 9 and the like. Further, the accumulator chamber 2 is formed at the rear end of the body 1 and there is provided a handle portion 13 having an air intake 16 to which an air hose 50 connected to an air compressor (not shown) is connected. A trigger 17 for controlling a trigger valve 14 is also provided near the handle portion 13.
The air hose 50 connected to the air compressor is connected to the air intake 16 at the rear end of the handle portion 13, so that the compressed air is accumulated in the accumulator chamber 2.
FIG. 14 shows the nailing machine in the initial state in which compressed air is accumulated in the accumulator chamber 2 before the nailing operation is performed, the trigger valve 14 making the accumulator chamber 2 communicate with the main valve upper chamber 15 via the air passage 9.
While the main valve 5 stays in the lower position as shown in the drawing, the communication between the inside of the cylinder 4 and the accumulator chamber 2 is shut off and an exhaust vent 10 in the upper position of the cylinder 4 is opened. Thus, the upper portion of the piston 8 in the cylinder 4 communicates with the atmosphere and the piston 8 as well as the drive bit 7 in the cylinder 4 is in the elevated position.
When the trigger valve 14 is operated after the trigger 17 is actuated as shown in FIG. 15, the communication between the main valve upper chamber 15 and the accumulator chamber 2 is shut off. Then the compressed air in the accumulator chamber 2 causes the main valve 5 to ascend, which makes the inside of the cylinder 4 communicate with the accumulator chamber 2 and shuts the exhaust vent 10. The compressed air that has flowed into the upper portion of the piston 8 in the cylinder 4 causes the piston 8 and the drive bit 7 to descend rapidly within the cylinder 4, whereby the nail 6 positioned in the ejection portion 12 is hit before being driven into a workpiece 19.
At this time, the compressed air flows into the return air chamber 3 via the air passage 11 provided in the cylinder 4.
When the operation of the trigger 17 is released so as to make the main valve upper chamber 15 and the accumulator chamber 2 communicate with each other after the trigger valve 14 is returned to the initial state, the main valve 5 descends and the compressed air above the piston 8 in the cylinder 4 is discharged from the exhaust vent 10 into the atmosphere. The piston 8 and the drive bit 7 are caused to ascend by the compressed air in the return air chamber 3, and the nailing machine returns to the initial state shown in FIG. 14.
The conventional nailing machine operates as mentioned above and since the compressed air in the accumulator chamber 2 flows into the cylinder 4 and the return air chamber 3 during the nailing operation and since the compressed air that has flowed therein is discharged into the atmosphere, the pressure in the accumulator chamber 2 is reduced as the nailing operation continues. However, as the accumulator chamber 2 is communicating with the air compressor via the air intake 16 and the air hose 50 provided at the rear end of the handle portion 13, the compressed air is supplied from the air compressor when the pressure in the accumulator chamber 2 is reduced. Consequently, the accumulator chamber 2 always holds the air pressure needed to perform the nailing operation and this makes it possible for the nailing machine to perform the nailing operation.
The nailing operation is made possible by the compressed air supplied from the air compressor as long as the aforementioned conventional nailing machine is concerned; in other words, the nailing operation cannot be performed unless the nailing machine is connected to the air compressor. Consequently, the air hose 50 is indispensable to connecting the air compressor to the nailing machine, which results in poor workability because the nailing machine is limited by the length of the air hose 50, the installation place of the air compressor and so forth.
When the nailing work is done in a small place, for example, the disadvantage is that the air hose 50 becomes obstructive.
One of the ways of obviating the above disadvantage is as disclosed in Japanese Utility Model Publication 13499/1973 to provide a nailing machine using liquified gas within a detachable liquified gas storage tank in its body as a power source. Although restrictions depending on the length of the air hose and the installation place of the air compressor and so forth are not imposed, many storage tanks will have to be prepared beforehand if the amount of work is large because it is difficult to refill the used storage tank with the liquified gas.
Another way of solving the above problem is to provide a nailing machine using a secondary battery as a power source but its power output is smaller than what is available from the compressed air as a power source, moreover, it takes much time to charge the secondary battery.